The present invention relates to a peeling machine. More particularly this invention concerns an upstream guide of such a machine.
As described in European patent document 0,462,322 of Glomb et al, a peeling machine for stripping mill scale and the like from a rod which may be tubular comprises an upstream guide, a central rotary scraper, a downstream guide, and a feeder for advancing the rod along its axis through the guides and scraper. The upstream feeder comprises a plurality of rollers bearing radially upstream of the scraper against the unscraped workpiece, and the downstream feeder can comprise another such array of rollers or slide blocks bearing radially against the scraped workpiece downstream of the scraper. The feeder has a plurality of jaws or rollers that are normally located downstream of the downstream guide and that pull the rod through the machine. The scraper itself comprises at least one scraping tool that is orbited about the axis between the two guides so as to cut an outer layer off the rod workpiece.
The guides need to hold the workpiece as steady as possible which is a fairly difficult task as it is moving longitudinally while being engaged forcefully in a radial direction by the tool or tools of the rotary scraper head. In particular the rapidly rotating scraper must not set the workpiece vibrating such that the tools dig excessively into it. The guides must damp this vibration as much as possible.
The standard biasing system for the upstream guide rollers is typically a respective pack of spring washers braced between each roller mount and a respective radially extending spindle threaded into a fixed support. Thus to increase the damping effect the spindle is advanced to compress the spring pack more, and to decrease it the spindle is retracted. Since the workpiece is relatively incompressible, such screwing-in or screwing-out of the spindle does not perceptibly move the respective roller appreciably, but changes the extent of compression of its biasing spring pack. Such systems often let the workpiece vibrate, a standing wave being created in it that is a function of the extent of compression of the spring packs, the rotation rate of the scraper head, the longitudinal displacement speed of the workpiece, the workpiece composition, and other minor factors.
It in therefore an object of the present invention to provide an improved upstream guide for a rod-peeling machine.
Another object is the provision of such an improved upstream guide for a rod-peeling machine which overcomes the above-given disadvantages, that is which substantially eliminates vibration in the rod so that the scraper can cut the rod to a perfectly cylindrical shape.
A peeling machine through which a rod workpiece is moved along a main axis has an upstream guide and a downstream guide centering the workpiece on the axis and axially flanking a rotary scraper engaging the workpiece. The upstream guide has according to the invention a plurality of supports angularly spaced about the axis and respective holders displaceable in the supports along respective holder axes extending radially of the axis and having respective centering elements engaging the workpiece radially of the main axis. Respective biasing units braced between the holders and the supports elastically press the elements against the workpiece radially of the main axis. Respective brake elements in the supports engage radially of the holder axes against the holders and are pressed radially of the holder axes against the holders so as to rub on the holders and damp vibration in the workpiece.
This system serves to damp even minor radial displacements of be workpiece so that the scraper will not dig into it, Whereas the prior-art system often allows the workpiece to move radially to a small extent, the system of this invention suppresses even these minor movements.
The brake elements according to the invention are formed as pistons and the means for pressing includes a source of hydraulic pressure operable against the pistons. The centering elements are rollers. The hydraulic-pressure source applies the same pressure to all of the pistons. The pistons are of a wear-resistant material such as bronze or red brass and have inner ends that are complementary to the outside shape of the holder. With a cylindrical sleeve-shaped holder the pistons engage over about 120xc2x0 of the holder in good surface-to-surface contact.
The biasing unit in accordance with the invention includes respective springs braced axially of the holder axes against the holders,